Selective inhibition by gossypol of endothelium-dependent relaxations augments relaxations to glyceryl trinitrate in rabbit coeliac artery.

1 Acetylcholine, substance P, prostaglandin E1 and the nitrovasodilator glyceryl trinitrate induced concentration-dependent relaxations of endothelium-intact strips of rabbit coeliac artery precontracted with noradrenaline. 2 Endothelium-denuded strip preparations contracted to acetylcholine and showed no response to substance P. The relaxant response to prostaglandin E1 was unimpaired after removal of endothelium, whereas the response to glyceryl trinitrate was increased. 3 A 20 min exposure of endothelium-intact strips to gossypol, an irreversible inhibitor of the production and/or release of endothelium-derived relaxing factor, abolished vasodilatation in response to the endothelium-dependent agents acetylcholine and substance P, did not change relaxations to prostaglandin E1, but significantly enhanced relaxations in response to glyceryl trinitrate. 4 In view of the assumed common mechanism of action of endothelium-derived relaxing factor and nitrovasodilators, these results suggest an interference of the two active principles at the level of the vascular smooth muscle cell.